Hello Dan, the best answer is to find at Google search but so far I searched about kimchi, none of them are not to use both of the napa cabbage’s parts. For me, it’s a waste if someone use only the leafy part instead of using both of them. Do your friend loves to eat that part only? :)

I’m sorry for the late reply! Yes, he loves kimchi but only the leafy part, not the firm part. I agree it would be wasteful to just throw away the rest of the cabbage but I’m sure he would find a use for it, probably in soup.